Potential ratio-controlled amplifier



` Aug- Z8, 1945. c. w. HANsELL POTENTIAL RATIO-CONTROLLED AMPLIFIERlllll' Patented Aug. 28, 1945* STAT POTENTIAL nario-common@ 'l'f'i ilAe? ci.

Application December 10, 1942, Serial No. 4468,449

V(Cl. Z50-20) 14 Claims.

My present invention relates generally to circuits for obtaining controlof the distribution of current between at least two electron collectionelectrodes, and more specifically to an electrically controlled devicefor controlling the distribution of current between a pair of -anodessubstantially in accordance with the ratio of two controlled potentials,or currents, independently of their amplitude.

In my application Serial No. 469,647 led Dec. 21, 1942, I have disclosedand claimed various devices for controlling the division of acurrentinto parts according to the ratio of two controlled curents. Briey, inthat application the circuit arrangements function in accordance 'withtheprinciple that when a magnetic eld in a Vacuum is made strong enoughsubstantial electron motions can take place only in the directionsparallel to the magnetic field. Any component of motion in otherdirections is overcome, because the magnetic eld bends the path ofmotion in these directions back to the axis from Ywhich they started.More specifically a pair of crossed magnetizing coils, within whichthere is located a cathode and an arangement of anodes, are provided,and the distribution of electron current to the anodes is-controlled byterms angular velocity-modulated carrier waves" and timing-modulatedcarrier waves are to .be understood as covering either frequency orphase modulated carrier waves, or combinations thereof. In thisconnection it is pointed out that frequency modulations of Aacarrieicurrent in which the higher modulation frequency currents are emphasizedor increased with respect to lower frequencies results in a type ofmodulation which is more accurately described as phase modulation thanas frequency modulation. Thus, the above terms are intended to includeany form of frequency modulation, or any form of phase modulation.

A still more speciiic object of my present invention is to providefrequency and phase modulation receivers without amplitude limiters, buthaving over-al1 characteristics similar to those v'obtainable throughthe use of limiters. In accomplishing this purpose I providesubsequently variations.

regulating the direction of the eld. The latter, f

in turn, is controlled by the ratio of currents in the magnetizing coilsindependently of the amplitude of these currents.

Accordingly, it' may be stated that it is one of the main objects of mypresent invention to provide a method of electrically controlling theKdistribution of current between a pair of anodes in accordance with theratio of two controlled potentials independently of their amplitude.

AIn my aforesaid application there is also disclosed the application ofthe electron current distribution method to a frequency, or phase,modulation receiver which does not employ a carrier -ing it unnecessaryto apply a special amplitude limiter stage in a frequency modulationreceiver. In this application, wherever used, the generic In using thephrase potential ratio-controlled I have assumed that the word ratio hasno other dimension or significance than magnitude. Consequently, I wishit to be understood that the expression "potential ratio inherentlysignifies the ratio of magnitude of two potentials.

Other objects of the invention are to improve generally the simplicityand eiciency of fre-v quency and phase modulation receivers, but moreespecially to eliminate any need for an amplitude limiter.

The novel features which I believe to be characteristic of my inventionare set forth in particularity in the appended claims; the inventionitself, however, as to both its organization and method of operationwill best be understood by reference to the following description, takenin connection with the drawing, in which I have indicateddiagrammatically a circuit organization whereby my invention may becarried into etl'ect.

s In the drawing:

Fig. 1 shows a circuit embodying the invention. Fig. 2 is a partlysectioned view of the interior of an amplifier tube adapted for use inthe circuit of Fig. 1,

Fig. 3 is a sectional view along line 3-3 of Fig. 2v looking inthedirection of the arrows,

Fig. 4 is a sectional view along line -B of Fig. 2, looking in thedirection of the arrows.

Referring, now, to the accompanying drawing, wherein like referencecharacters in the different figures designate similar circuit elements,the circuit of Fig. 1 shows the invention applied to afrequencymodulated carrier wave (FM) receiver. More speciilcalLv. thepotential ratio-controlled amplifier tube I is utilized subof frequencyand phase modulated radio waves,

of which reception of FM radio broadcast programs is a common example,there are undesired amplitude modulations of carrier currents in thereceivers which tend to add unwanted noise to the receiver output. Theseamplitude modulations usually are present because of hum'modulations inthe transmitter; because of interfering radiations produced from thespace circuit due to natural causes, or due to operation of electricalequipment of many kinds; because of hum and microphonic noises in thereceivers; because of thermal agitation and shot effect noises in earlycircuits in the receivers; and because of insuflicient uniformity, orfiatness of response, of selective circuits within the frequency bandoccupied by the frequency and phase modulated waves and currents. In theprior art it has been customary to employ an amplitude limiter forremovingamplitude modulations from the carrier current before thecarrier current is applied to a frequency or a phase modulationdemodulator. By removing amplitude modulations with a limiter it hasbeen found possible to make a very substantial improvement in signal tonoise ratio in the output of frequency and phase modulation receivers.

The following patents are given to illustrate .the state of the priorart of receiving frequency and phase modulated carrier waves. It is tobe understood that the presently disclosed potential ratio-controlledamplifier circuit may be used in any of these prior systems. Thisinventionis of broad application, and may be utilized with otherapparatus of widely varying characteristics including any of the priorsystems described in the following patents. The latter are arranged inthe order of filing of the respective applications: U. S. Patent No.2,057,640, Conrad, filed Mar. 17, 1927; U. S. Patent No. 1,941,447-,Armstrong, filed May 18, 1927: U. S. Patent No. 1,819,508. Hansell,filed Aug. 11, 1927; U. S. Patent No. 1,794,932, Usselman. filed Sept.1, 1927; U. S. Patent No. 2.013,847, Hansell. filed Oct. 2, 1928; U. S.Patent No. 1,803,504, Hansell. filed Oct. 5. 1928; U. S. Patent No.1,867.567, Hansell.

led Feb. 1, 1929; U. S. Patent No. 1.941,069,'

Armstrong, filed Jan. 24, 1933; U. S. Patent No. 2.121.103, Seeley, ledOct. 17. 1935: U. S. Patent No. 2,180,736, Hansell, filed May 5, 1936:U. S. Patent No. 2 205,762. Hansell. filed Nov. 16, 1936; U. S. PatentNo. 2,179,182, .Hansell. filed Nov. 27, 1936; U. S. Patent No.2,207,541. Hansell, filed Jan- 18, 1939; U. S.,Patent No. 2,243,702,Hansell, filed May 19, 1939; and U. S. Patent No. 2,249,425, Hansell,filed Mar. 27, 1940.

The limiters of the prior art have usually been some sort of amplifierso designed, adjusted and operated that changes in input power gavelittle, if any, change in output power. These limiters required someinput power level to be exceeded before a satisfactory hunting conditionwas reached, and often they showed a reduction in output power if theinput power became relatively high. In designing limiters it has beenfound that the amplifier-limiter system preceding the demodulator mustbe capable of great over-al1 amplification, or increase of power, whenweak signals are to be received. To provide for this turers, to avoidthe cost, have sold frequency modulation receivers to the .public whichomitted amplitude limiters even though such receivers do hors adequatelysuppress amplitude modulation no e.

In my application Serial No. 423,881, filed December 22, 1941, there aredisclosed various types of demodulators for frequencyand phasemodulation wvhioh when provided with a correct level of input power, areinherently unresponsive to the eil'ects of amplitude modulation so thatno limiter is required. Inthe present application the frequency or phasemodulation receiver may be of any of the prior systems noted, save thatthey do not include a special amplitude limiter prior to the detector.In accordance with my present invention the detector may be of anywell-known form. Instead of constructing the demodulator to beinherently unresponsive to amplitude modulation, I provide an amplifiercircuit subsequent to the demodulator, which ampli` fier circuit isunresponsive to the amplitude modulation. The demodulator tubes areshown as consisting of a pair of opposed diode rectiiiers 2 and 3. TheFM signals. regardless of the source thereof, are applied to an inputtransformer I.

One end of the secondary winding of the transformer is connected to thejunction of a pair, of series-related series resonant circuits. One ofthese series resonant circuits consists of condenser 5 and coil 6. Theother series resonant circuit consists of coil 'I and condenser 8. 'Ihejunction of'coil 8 and 'l is connected to the aforementioned end of thelsecondary winding of transformer 4. The anode of rectifier 3 isconnected to condenser 5, and to the opposite end of the secondaryWinding of transformer 4 through a resistor 9. Theanode of rectifier 2is connected to condenser 8, and to the last mentioned end of thesecondary winding throughv resistor I0.

The output load resistors of the rectifiers 2 and 3 are designated bynumerals II and I2 respectively. Each of these load resistors isbypassed by an appropriate radio frequency by-pass condenser. Thejunction of resistors I2 and II is connected to the junction of coil 6and 1. The

.Y v n '2,383,855 theArmstrong patent, the series resonant cirpotential,to the discriminator series resonant circuits within the signallingband, even though the series resonant circuits change impedancef withchange Vof frequency. f

It has been stated before that the series resonant circuits -6 and '1 -8are oppositely mistuned by substantially equal frequency amounts withrespect to the center frequency Fc of the applied FM waves. While it isnot believed necessary to give specific' frequency values, those skilledin the art know that for receiving standardized FM transmitters in theUnited States the frequency of circuit E-dmay be removed some '15kilocyclesv (kc.) or more from Fc. The frequency of circuit 1 8 may becorrespondingly located 'l5 kc. or more on the opposite side of Fc.-However, by tuning the series resonant circuits apart by a greateramount, and utilizing sufllciently broadly tuned circuits, lessdistortion in the demodulated output from the demodulator may beobtained. Thus, by broadening the circuit tunings and setting the tuningpeaks further -apart in frequency in a manner to reduce the percentagedifferential response of the circuit to a given change of frequency, thedistortion of the detector network output may be reduced. Additionalinfomation on this subject will be found in my application Serial No.297,777 led vCoto-- ber 4, 1939, which is a division of my U. S. Patent2,179,182 grantedNoVember 7, 1939.

Where the receiving system is of the superheterodyne type, which is thetype universally anployed in present-day FM broadcast reception, theinput circuits ofV the rectifierv tubes will be operating at a lower, orI. F., value. Such I. F. value would generally be chosen from a range ofbetween 2 and 8 megacycles -(mc.) The assigned FM broadcast band in theUnited States at the present time is 42 to 50 mc., and the rmissiblechannel width is 200 kc. As is well known, a carrier is deviated amaximum of substantially 75 kc. to either side thereof, and, hence, inthe Vbest receivers the inter-tube networks preceding thedemodulator-are designed to transmit nearly equally a band width ofapproximately 15o kc plus twice the band width of the modulationfrequencies. It will be understood that the primary circuit of inputtransformer li, which is magnetically coupled to the 'series resonantciircuits, Vwill be tuned to Fc, but will be a broad band circuitcapable of responding substantially equally to the whole signal band.

The primary circuit of transfermer t may be arranged in the anodecircuit of the last I. F. amplier stage. It is not believed necessarytodetially constant current, for any constant input has imposed thereonamplitude modulation components. Therefore, injthe output circuit of therectiflers, and prior to the input electrodes of tube l, there willappear the undesired amplitude modulation components. Nevertheless, theconstruction and functioning of tube i are such that in the outputcircuit thereof the amplitude mod-- ulation components will not appear,or will be of greatly reduced relative strength. It will be recognizedthat this is entirely different from the:

practice which has been followed in the priorart departedfrom'by theaforementioned instantane-l It is not believed necessary to explain themanner in which the detector functions. It is sufficient to point outthat when the signal energy l il and l2 will have like polarity. Whenthe in. stantaneous frequency of the applied signal en-Y erg-y shiftsaway from Fc, there will be developed across one vol the load resistorsmore rectified potential. Of course, that load resistor will have a.greater magnitude of rectied potential thereacross which corresponds tothe series resonant input circuit whose resonant frequency is being ousfrequency. In other words, for frequency deviation from Fc, the cathodeends of resistors H and l2 will be of like polarity, but of unlikemagnitude. Of course. the carrier amplitude variations will affect bothends of resistors il and I2 to substantially the same percentage magni-It is to be understood that the present invention is applicable to anyother type of balanced FM detector circuit. For example, the resistorsHand I2 could be placed in the output circuits of the demodulatordisclosed in the aforementioned Usselman patent. Again, the resistors.could be placed in ,the outputfcircuits ofthe demodulator described'inthe aforementioned Seeley patent. fr,

includes the potential ratio-controlled amplier. `The amplifier tube Iis schematically represented in Fig. l. In Figs. 2, 3 and 4 theelectrode structure thereof is more specifically shown. In general,the,tube l is of the type shown in my application Serial No. 324,053filed March 15, 1940. y

However; there' are certain modications and improvements involved in thetube 'structure as well as in the use of the tube in this presentapplication. v

Within the tube envelope of tube i there is provided an electronemission element i3, which 'has the electron stream therefrom passedscribed the networks between the conventional v signal collector andtransformer 6, since these may follow standard FM broadcastsuperheterodyne receiver practice. Those skilled in the art are fullyaware of the construction thereof. It is to beclearly understood that inthe present case no amplitude limiter need be utilized in the systempreceding the input to the demodulator at the primary winding oftransformer 4. When no limiter is employed, it will be clear that therewill be impressed upon the series resonant circuits 5-.6 and '--SV theFM waves whose carrier Y trodes 20 and 2l.

minal of potentiometer P. A ,shield electrode,

projects from the end I9 of cylindcr'electrode I8,

and acts as an electrical shield between elec- The cylinder I8 isconnected t0 potential point I5, and hence, is at the same potential asanode Il. The forward end of cylinder I8 is open so that the electronbeam readily passes through the open end into the field betweenelectrodes Il and I6. The electrodes I'I is connected to the cathode endo! resistor I2 by condenser 30, while condenser 3I couples the electrodeI6 to the cathode end of resistor II.

Resistor 32 is connected in shunt with load resistor II-I2, and betweencondnsers 30 and 3|.

'Ihe midpoint of resistor 32 is connected to a point 33 on P which is ata negative potential relative t0 point I5. Hence, the electrodes I'I andI8 are normally, and in the absence of applied signals, at an equaldirect current potential which is less positive than point I5 and thepositive end of potentiometer P. Before explaining the functioningr ofthe potential ratio-controlled amplifier circuit, the detail structureof the tube will be considered. As stated previously, the representationof tube IV in Fig. 1 is purely schematic. Hence, Figs. 2, 3 and 4 shouldbe considered in connection with tube I.

'I'he tube envelope 40 may be made of glass, metal or other suitablematerial. Preferably, the envelope has a constricted section in which islocated the electron emitter I3 and heater element I3'. The anode Il isshown as a hollow cylinder surrounding the emitter. 'I'he electrons areprojected into the iiared main body of the tube through the aperture I4'in the forward end of the anode. The electrodes I6 and lI'I are eachlong rods, of circular cross-section. They diverge in the manner shownin Fig. 2. Leadsv Il' and I8' connect rods I'I and- I6 respectively tocoupling condensers 30 and 3l. The numeral 50 denotes the electron beamwhich passes to the end I9 of the shield can I8. The can I9 is metal#lic, as are the rods I'I and I6. 'Ihe can I9 tag pers towards its openinput end. Since the shield I8 is a hollow cylinder which envelopes therods I1 and I6,1the closed end I9 has a circular shape.

'I'he end wall I9 is provided with a circular screen I9', 0r grid-likemesh, through which electrons may pass to the spaced collectorelectrodes and 2|. The screen has its wires preferably parallel to thedirection of beam deilection. Across the diameter of the screen I9 issecured a lateral metallic, electric shield 23. 'Ihe latter is located5between the collectors 20 and 2|. in spaced relation thereto. Eachcollector is a hollow box. One long side of the box is open, and spacedfrom the foraminous screen I9. The conductors from the collectors passto respective opposite ends of the primary winding of audio transformer22. Fig. 4 shows the relation between the electrodes when viewed fromthe collectors towards the emission electrode. The electrlc shield 23extends beyond the limits of the spaced parallel collectors. Theconductors from the collectors 20 and 2l are designated by the numeralBI. These conductors are connected to the respective ends of the primarywinding of audio transformer 22.

Referring to Fig. 3 there is shown in cross-section the electrodes I8,II and I8, and the approximate coniiguration of an electric ileidbetween them. Flg. 3 shows how the enveloping cylinder- I8 surrounds thetwo Vrod-like electrodes I'I and I8. The electrodes Il and Il areindicated as negatively charged with respect to the cylindricalelectrode I 8A With this arrangement as it is indicated in Fig. 3, therewill be a region of substantially zero transverse electric field midwaybetween the two rods IB and I'I. This region of zero 'transverseelectric Ileld can be moved toward or away from each of electrodes I6and Il by giving to the latter a diierence in negative potential. As hasbeen explained previously, the electrodes I8 and I1 are connected topoint 33 of potentiometer P, point 33 being asubstantially negativepotential point.

Assume, now, that a stream of electrons is passing' along the axis ofthe cylindrical electrode I8 midway between the two rod electrodes I 8and II. There will be substantially no tendency for the electron streamto be accelerated in any transverse direction so long as itis travelingin the region of substantially zero transverse electric field. However,if for any reason the stream is deilected toward one or the other of therod-like electrodes, it will come within an electric iield which tendsto return it to the line, or region, of zero electric ileld.

Therefore, to aiair degree of approximation,

when the potentials on electrodes I 6 and Il are angles to a lineconnecting the electrodes I6 and II'. In other words, the electronstream 50 is constrained to ow within the region o1' substan tially zerotransverse electric eld. Accordingly, if we apply diierent electricpotentials to the electrodes .I6 and I1, thereby deflecting the regionoi' zero transverse electric field, the path which can be taken by theelectron stream may be controlled. Within a large range of potentialsthis path may be made substantially independent of the total potentialsupon the rod electrodes with respect to the cylindrical electrode I8,but dependent substantially upon their ratio. 'I'hat is why theamplifier I has been referred to as a potential ratio-controlledamplier.

Therefore, if the negative potential applied to each of electrodes I 6and Il is obtained from one side of a balanced FM detector, it ispossible to make the path taken by the electron streams substantiallydependent upon the frequency of current input to a balanced FM detector,but nearly independent of the amplitude of signal input to the balanceddetector. It is to be clearly understood that while I have shown a,particular type of amplifier tube construction for tube I, other typesof tube structure operating on the same principles may be used. Forexample, any of the tube structures shown in my aforesaid pendingaplication Serial No. 324,053 may be-utilized in place of the particulartube structure shown herein. Again, it is to be understood that thedetail conilgurations of the electrodes I6, I1 and I8 are not essential,since other coniigurations may be utilized. For example, the rodelecaasaeas l Y organization shown and described, but that many2modiiic'ations may be made without departing from the scope of myinvention, as set forth in the appended claims.

What I claim is: 1. In combination with a detector of angularvelocity-modulated carrier waves adapted to produce a pair ofindependent voltages which corre- Y spond to modulation of the carrierwaves, and

which voltages are of like polarity relativeto a. common referencevoltage point but of diierent 'magnitude,' an electron discharge tubecomprising an electron emission element, a pair of elec- Y troncollector electrodes, a modulation voltage utilization circuit coupledto said `collector electrodes, means-conning the electrons emitted fromsaid emission element to an electron beam projected toward saidcollector electrodes, at least two beam control electrodes in4 spacedrelation on oppostie sides of said beam, said control electrodesdivergi'ng in the direction of said collector electrodes, means forapplying the aforesaid modulation voltages of differing magnitude torespective ones of said control electrodes, and means for maintainingsaid spaced control electrodes at a normal negative potential withrespect to said collector electrodes whereby said electron beam is`constrainedto ow within a limited region between the two controlelectrodes.

A2. In combination with a detector of angular velocity-modulated carrierwaves adapted to produce a pair of independent voltages which correspondto modulation of the carrier waves, and which voltages are of likepolarity relative to a common reference voltage point but of differentmagnitude, an electron discharge tube comprising an electron emissionelement, a pair of electron collector electrodes.. a modulation voltageutilization circuit coupled to said collector electrodes, meansconfining the electrons emitted from said emission element to anelectron beam projected toward said collector electrodes, at least twobeam control electrodes in spaced relation on opposite sides of saidbeam, said control electrodes diverging in the direction of saidcollector electrodes, means for applying the aforesaid modulationvoltages of differing magnitude to respectiv'e ones ofsaid controlelectrodes, means for maintaining said spaced control electrodes at anormal negative potential with respect to said collector electrodeswhereby said electron beam is constrained to flow within a region midwaybetween the two control electrodes, and a cylindrical electrodesurrounding said spaced control electrodes, said cylindrical electrodebeing maintained at a positive potential with respect to the potentialsof said spaced control electrodes.

3. In combination with a balanced frequency modulation' carrier wavedetector adapted to provide 'a pair of independent modulation voltagesof like polaritrr relative to a. common reference voltage point anddiiering magnitude, an amplifier tube for said modulation voltage whichis insensitive to carrier amplitude variation, said amplier comprisingan lelectron emission element, means for producing an electron beam fromelectrons emitted from said element, a pair of spaced rod-likeelectrodes arranged on respectively opposite sides .of the electron beamand being divergent.. a pair of spaced collector electrodes, amodulation voltage utilization circuit connected in push-pull relationto said collector electrodes, a hollow cylindrical electrode envelopingsaid rodlike electrodes, means for maintaining the latter electrodes ata. negative potential relative to the enveloping cylinder vand saidcollector electrades whereby said-electron beam passes along the axis ofthe cylindrical electrode midway between the rod-like electrodes, andmeans for ap- Plyns the aforesaid modulation voltages to the lrespective ones of said rod-like electrodes. said cylindrical electrodehaving the end thereofadjacent said collector electrodes provided-withan electron-transmitting screen. 4. In combination with a detector ofangular velocity-modulated carrier waves adapted to produce a pairof'independent voltages which correspond to modulation of the carrierwaves, and which voltages are of like polarity relative toa commonreference voltage point but of diierent magnitude, an electron dischargetube compi'fis-A ing an electron emission element, a pair of electroncollector electrodes. armoclulation voltage utilization circuit coupledto said collector electrodes, means conning tne electrons emitted fromsaid emission element to an electron beam projected toward saidcollector electrodes, means for establishing an electric field whichforces electrons in the beam toward a plane of minimum transverseelectric eld, and means for applying the aforesaid modulation voltagesof diiering magnitude to vary the electric iield for varying theposition of the plane. l x

5. In combination with a'detector of angular velocity-modulated carrierwaves adapted to produce a pair of independent voltages which correspondto modulation of the carrier Waves, and which voltages are of likepolarity relative toa y common reference voltage point but of differentmagnitude, an electron discharge tube comprising an electron emissionelement, a pair of electron collector electrodes, a modulation voltageutilization circuit coupled to said` collector electrodes. meansconini'ng the electrons emitted from said emission element to anelectron beam projected toward said collector electrodes, at least twodivergent control electrodes in spaced relation on opposite sides ofsaid beam, means for applying the aforesaid modulation voltages `ofdiiering magnitude to/respective ones of said control electrodes, meansfor maintaining said'spaced control electrodes ata potential withrespect tosaid collector electrodes whereby said electronbeam isconstrained to now within a region midway between the two controlelectrodes, a .cylindrical y electrode surrounding said spaced controlelectrodes, and said cylindrical electrode being maintained/ at a.positive potential with respect to the potentials of said spaced controlelectrodes.

6. In combination with a detector of frequency modulated carrier wavesadapted to produce a pair of independent voltages which correspond tomodulation of the carrier waves, and which voltages are of like polarityrelative to a common reference voltage point but of different magnitude,an electron discharge tube comprising an electron emission element, apair of electron collector electrodes, a modulation voltage utilizationcircuit coupled to said collector electrodes, electrons emitted from.said emission element being in the region thereby to deflect theposition of the beam.

7. In combination with a balanced detector oi frequency modulatedcarrier waves adapted to lproduce voltages of differing magnitude whlchcorrespond to modulation of the carrier waves, an electron dischargetube comprising an electron emission element, a pair of collectorelectrodes, a modulation output ciruitcoupled to said collectorelectrodes, meaiisk'ning the electrons emitted from said emissionelement into an electron beam projected toward said collectorelectrodes,- at least two control electrodes in spaced relation onopposite sides of said beam, said control electrodes diverging towardssaid collector electrodes, means for applying the aforesaid modulationvoltages to respective ones of said control electrodes, and means formaintaining said spaced control electrodes at a potential with respectto said collector electrodes such that Said electron beam is constrainedto flow within a limited reslon between the two control electrodes.

8. In combination with a source of a pair of independent voltages oflike polarity relative to a common reference voltage but of diilerentmagnitude, an electron discharge tube comprising an electron emissionelement, a pair of electron co1- lector electrodes, an output circuitcoupled to 'said collector electrodes, means confining the electronsemitted from said emission element to an electron beam projected towardsaid collector electrodes,

' at least two beam control electrodes in spaced relation on oppositesides of said beam, said control electrodes diverging in th'e directionof said collector electrodes, means for applying the aforesaid voltagesof diilering magnitude to respective ones of said control electrodes,means for maintaining said spaced control electrodes at a normalnegative potential with respect to said collector electrodes wherebysaid electron beam is constrained to flow within a region midwayAbetvveen the two control electrodes, and a cylindrical electrodesurrounding said spaced control electrodes, said cylindrical electrodebeing maintained at a positive potential with respect to the potentialsof said spaced control electrodes.

9; In an ampliiier system which is insensitive to current amplitudevariation, an electron emission element, means for producing an electronbeam from electrons emitted from said element, a pair of spaced rod-likeelectrodes arranged on respectively opposite sides oi' the electron beamand being divergent, a pair of spaced collector electrodes, a voltageoutput circuit connected in pushpull relation to said collectorelectrodes, a hollow cylindrical electrode enveloping said rod-1ikeelectrodes, means ior maintaining the latter electrodes at a negativepotential relative to the enveloping cylinder and said collectorelectrodes whereby said electron beam passes along the axis of thecylindrical electrode midway between the rod-like electrodes, means forapplying voltages to be amplied to the respective ones of said rodlikeelectrodes, said cylindrical electrode having the end thereof addacentsaid collector electrodes provided with an electron-transmitting screen.

10. -In combination with a balanced frequency -modulation detector, anamplier insensitive to amplitude variation oi detected voltages, saidampller including a pair of spaced rod-like elecaplane of minimumelectric iield'in directions transverse to the general direction of thebeam,

and means to vary th'e ratio of the potentials.

11. In combination, an electron discharge tube comprising an electronemission element., a pair of electron collector electrodes; a signalvoltage utilization circuit coupled to said collector electrodes,electrons emitted i'rom said emission element being inthe form of anelectron beam projected toward said collector electrodes, means forestablishing a region of lowtransverse electric neld through which said-beam is constrained to pass, and means for utilizing signal voltages ofdiii'ering magnitude to move the position of the region thereby toideilect the position of the beam. r

l2. In a receiver of angular-velocity modulated carrier waves, ademodulator for producing a pair of independent modulation voltages fromsaid waves, anv ampliiler following the demodulator,

. said amplifier including means to provide an electron beam.,v meansfor establishing a region of low transverse electric field through whichsaid electron beam is constrained to pass, and means responsive to saidvoltages to move the position of the region to deect the position oi'the beam.

13. In combination with a detector of angular velocity-modulated carrierwaves adapted to produce a pair of independent voltages which correspondto modulation of the carrier waves, and which voltages are of likepolarity relative a reference vol-tage .point but of diiterentmagnitude, an electron discharge tube comprising an electron emissionelement, a pair of electron collector electrodes, a modulation voltageutilization circuit coupled to said collector electrodes, means forestablishing an electric field which forces electrons inthe beam towarda plane of minimum transverse electric eld, and means for varying theelectric iield in response to said voltages for varying the position ofthe plane.

14. In an electronic system, means' adapted to provide at least twopotentials, an electron vacuum tube including means for producing a beamof moving electrons. means i'or establishing a, configuration ofelectric elds within said tube which tend to determine the path' of theelectrons and to oppose any motions away from said path, at least twospaced electrodes responsive respectively to said potentials formodifying the coniiguration of the electric elds to bend the path, atleast two anodes in said tube for collecting the electrons with adistribution of numbers between the anodes which is determined by thebending of the patiiA in response to the ratio of said two

